[llvm] [InstCombine] Allow folds of shifts by constants for scalable vectors again (PR #132522)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Can we generally accept scalable splats in m_ImmConstant? I doubt this is the only place with this problem.

https://github.com/llvm/llvm-project/pull/132522